grantor:
University of TorontoThe effects of surface evaporation on the onset of oscillatory thermocapillary convection in half floating zones were studied experimentally. Thermocapillary convection was investigated in half-zones (D = 7.0 mm) using acetone and methanol as working fluids. The half-zones were either fully enclosed with a quartz tube or partially open to the ambient air, to change the evaporation rate. Experiments were conducted using various measurement techniques to determine the characteristics of thermocapillary convection during steady to oscillatory transition. Experimental results showed that the liquid temperature and surface velocity start to periodically fluctuate at the onset of instability. There was also a manifestation of vortex expansion and contraction in images obtained by Particle Image Velocimetry, and an appearance of a thermal wave traveling on the surface in infrared images. Heat loss by evaporation was found to strongly stabilize thermocapillary convection and reduce the critical Marangoni number as predicted by a linear stability analysis.M.A.Sc
